The present invention relates in general to adjusting the inductance of an air-core coil, and more specifically to an automated procedure for adjusting an air-core coil to achieve a desired operation in a circuit.
An air-core coil is an inductor comprised of one or more turns of wire which contains no magnetic core material inside the turns. Most typically, these coils are cylindrically shaped with circular turns (i.e., solenoidal) and contain only air in their interior. They are often used in electrical circuits to provide filters and tuned circuits.
The inductance of a solenoid-shaped coil is proportional to the volume defined by the turns and to the square of the number of turns per unit length. Therefore, it is possible to construct an air-core coil having an inductance approximately equal to a desired design inductance.
Air-core coils usually provide a fixed value of inductance in a circuit. However, it is known to alter the shape of an air-core coil to precisely "tune" a coil whereby the coil inductance can precisely match a desired value of inductance. For example, U.S. Pat. No. 2,722,662, issued to Tyminski, discloses an air-core coil wherein the coil can be adjusted either by compressing or expanding the spacing between coil windings or by bending the coil at an angle by as much as 180.degree. to decrease the coil inductance.
It is well known that manufacturing costs can often be decreased by employing automated manufacturing techniques. In fabricating large numbers of electrical circuits, such as ones using a printed wiring board, the use of automated manufacturing, adjustment and testing techniques is desirable. However, prior art adjustment techniques for air-core coils are not suitable for automated adjustment. For example, adjustment of coil inductance to both higher or lower values by compression or expansion of the coil length would require complicated mechanisms.